What Causes Obesity? Answer May Affect Your Waistline

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People's beliefs about what causes obesity may affect their
waistlines, according to a new report.

People who named a lack of exercise as the main
cause of obesity were more likely to be heavier than those
who blamed a poor diet, according to the findings.

"Across multiple studies, we found the first evidence that people
generally have two different lay theories about what causes
obesity, and that these beliefs impact people's actual likelihood
of being overweight," wrote the study authors, led by Brent
McFerran, a marketing professor and social psychologist at the
University of Michigan in Ann Arbor.

More than two-thirds of adults in the United States are
overweight or obese, according to the Centers for Disease Control
and Prevention. While research suggests that a sedentary
lifestyle and genetics play roles in causing obesity, a large
body of scientific evidence points toward overeating as the main
culprit, the researchers said.

Those who said diet was the main cause had an average body mass
index (BMI) of 21.55, significantly lower than the average BMI of
23.10 among those who said a lack of exercise was obesity's main
cause. (A BMI of 25 or higher is considered overweight, and a BMI
of more than 30 designates obesity.)

The researchers also found similar trends among residents of the
U.S. and France, suggesting that
beliefs about obesity and weight loss are cross-cultural.

In another test in the new study, nearly 100 Hong Kong college
students were asked to snack on chocolates while they completed a
survey. Researchers "primed" the students prior to the survey by
reading a passage about either exercise or eating as the main
cause of obesity.

The researchers found that students who were primed with an
exercise theory of obesity ate significantly more chocolates than
students primed with a diet theory.

The findings show that people's beliefs about what causes obesity
can influence eating habits, the researchers said.

"Our results echo a lot of medical research that changing one's
diet is a much easier way to shave off calories than going to the
gym more often," McFerran said. The study was published this
month in the journal Psychological Science.

Though the researchers accounted for some factors that could
explain the effects on BMI, such as level of education and age,
they can't say for sure whether some other factor played a role
in the results.

It's also possible that a person's BMI could affect which theory
he or she found more plausible. For instance, trying to lose
weight by eating less, but not succeeding, could lead someone to
put more stock in exercise as the answer to weight loss.

"This study is an example of how detached we have become from
what we eat," said Dr. Mitchell Roslin, chief of weight-loss
surgery at Lenox Hill Hospital in New York. "We define ourselves
by what we do — as writers, doctors, firemen — but we each only
have one body. We must start defining ourselves by our health."

But Roslin, who was not involved in the study, said the study's
usefulness in practice may be limited. "Psychologists have been
trying for years to identify an obese personality that could help
with behavioral counseling, but this study doesn't do that," he
said. "Obesity is very complex. There is no one personality
type."